JAVA-5788 Latin heap array fast path

bson/src/main/org/bson/ByteBuf.java

@@ -125,6 +125,13 @@ public interface ByteBuf  {
      */
     ByteBuf flip();
 
+    /**
+     * States whether this buffer is backed by an accessible byte array.
+     *
+     * @return {@code true} if, and only if, this buffer is backed by an array and is not read-only
+     */
+    boolean hasArray();
+
     /**
      * <p>Returns the byte array that backs this buffer <em>(optional operation)</em>.</p>
      *

bson/src/main/org/bson/ByteBufNIO.java

@@ -103,6 +103,11 @@ public ByteBuf flip() {
         return this;
     }
 
+    @Override
+    public boolean hasArray() {
+        return buf.hasArray();
+    }
+
     @Override
     public byte[] array() {
         return buf.array();

bson/src/main/org/bson/io/OutputBuffer.java

@@ -196,11 +196,15 @@ public void writeLong(final long value) {
         writeInt64(value);
     }
 
-    private int writeCharacters(final String str, final boolean checkForNullCharacters) {
+    protected int writeCharacters(final String str, final boolean checkForNullCharacters) {
+        return writeCharacters(str, 0, checkForNullCharacters);
+    }
+
+    protected final int writeCharacters(final String str, int start, final boolean checkForNullCharacters) {
         int len = str.length();
         int total = 0;
 
-        for (int i = 0; i < len;) {
+        for (int i = start; i < len;) {
             int c = Character.codePointAt(str, i);
 
             if (checkForNullCharacters && c == 0x0) {

driver-core/src/main/com/mongodb/internal/connection/ByteBufferBsonOutput.java

@@ -16,6 +16,7 @@
 
 package com.mongodb.internal.connection;
 
+import org.bson.BsonSerializationException;
 import org.bson.ByteBuf;
 import org.bson.io.OutputBuffer;
 
@@ -27,6 +28,7 @@
 
 import static com.mongodb.assertions.Assertions.assertTrue;
 import static com.mongodb.assertions.Assertions.notNull;
+import static java.lang.String.format;
 
 /**
  * <p>This class is not part of the public API and may be removed or changed at any time</p>
@@ -273,6 +275,42 @@ public void close() {
         }
     }
 
+    @Override
+    protected int writeCharacters(final String str, final boolean checkForNullCharacters) {
+        ensureOpen();
+        ByteBuf buf = getCurrentByteBuffer();
+        int i = 0;
+        if (buf.hasArray() && (buf.remaining() >= str.length() + 1)) {
+            byte[] array = buf.array();
+            int pos = buf.position();
+            int len = str.length();
+            for (;i < len; i++) {
+                char c = str.charAt(i);
+                if (checkForNullCharacters && c == 0x0) {
+                    throw new BsonSerializationException(format("BSON cstring '%s' is not valid because it contains a null character "
+                            + "at index %d", str, i));
+                }
+                if (c > 0x80) {
+                    break;
+                }
+                array[pos + i] = (byte) c;
+            }
+            if (i == len) {
+                int total = len + 1;
+                array[pos + len] = 0;
+                position += total;
+                buf.position(pos + total);
+                return len + 1;
+            }
+            // ith character is not ASCII
+            if (i > 0) {
+                position += i;
+                buf.position(pos + i);
+            }
+        }
+        return i + super.writeCharacters(str, i, checkForNullCharacters);
+    }
+
     private static final class BufferPositionPair {
         private final int bufferIndex;
         private int position;

driver-core/src/main/com/mongodb/internal/connection/CompositeByteBuf.java

@@ -208,6 +208,11 @@ private int getShort(final int index) {
         return (short) (get(index) & 0xff | (get(index + 1) & 0xff) << 8);
     }
 
+    @Override
+    public boolean hasArray() {
+        return false;
+    }
+
     @Override
     public byte[] array() {
         throw new UnsupportedOperationException("Not implemented yet!");

driver-core/src/main/com/mongodb/internal/connection/netty/NettyByteBuf.java

@@ -95,6 +95,10 @@ public ByteBuf flip() {
         return this;
     }
 
+    public boolean hasArray() {
+        return proxied.hasArray();
+    }
+
     @Override
     public byte[] array() {
         return proxied.array();